"Vol. 67.] ANNIVERSARY ADDRESS OF THE PRESIDENT. lxxi 



If it should happen that the lines of maximum uplift have been 

 so situated as to cut off rain-bearing winds from the lower-lying 

 lands, so that desert conditions arise, then denudation due to inso- 

 lation and frost will be so rapid — compared with chemical action — 

 that there will be little decomposition of the more stable minerals. 

 Only the more soluble ingredients will be removed from the 

 minerals most easily broken down, and the detritus mechanically 

 transported will consist of fresh and unweathered minerals. This 

 has been well demonstrated by the observations of Prof. Judd on 

 the <S~ile muds, and by those of Dickson and Holland on the glacial 

 muds of the Alps. Tt has also been found that the coarser detritus 

 in such deposits as the Triassic skerries formed round the wind- 

 smoothed rocks of Mountsorrel and other Leicestershire areas is in 

 a precisely similar condition. 



At the same time, the salts that are dissolved are often not 

 carried outside the area of inland drainage, but are deposited in 

 the lakes and pools, or thrown down as crusts upon, or cements 

 among, the materials of the drier areas. The latter must often 

 take place where the water-bodies have outlets which lose them- 

 selves in the sandy and desert areas. It is possible that the 

 dolomite crystals found by Dr. Cullis and Mr. Bosworth in the 

 Keuper Marls may, in part, have some such origin. 



(cl) 'Estuarine Period.' 



(4) There will, as a rule, be a sharp contrast between the fea- 

 tures produced when uplift is taking place, and those which are in 

 existence when re-submergence follows the terrestrial phase. The 

 tectonic structures that are being formed are all submitted to the 

 rasping action of marine erosion as they rise ; and the emergent 

 land consists in part of planed folds, and in part of flat or gently 

 inclined sediments. But during the terrestrial phase the rock- 

 structures are dissected by subaerial denudation, originating features 

 of lively relief which, on submergence, will cause corresponding 

 diversity of contour. The rising coast will be one of sea-flats and 

 deltas, the subsiding coast one of gulfs and estuaries. 



Fiat areas of completed erosion and planes of lacustrine, desert, 

 or loess, deposition will, on submergence, be the first to receive new 

 sediments. The edges of these deposits will creep up to the 

 uneroded mountain framework, and will pass rapidly into shallow- 

 water and marginal sediments. As submergence proceeds there 

 will be rapid overlap of coarser by finer material, each sheet of 

 which will, however, be edged by its coastal representative. Such 



